Reporter: As police begin investigating the case against ma'lik richmond and trent mays, they can't rely on the victim, 16-year-old jane doe, who has no memory of the assault. Instead, they parade a who's-who of steubenville teenagers in to be questioned about what really happened that fateful summer night. Among them are honor students and athletes, many of whom knew of the crime. Some of whom even saw it, but none of whom thought to call authorities or a parent. We needed their testimony. It was crucial. Reporter: Prosecutors say the night begins with this, a tweet from trent early in the evening -- "huge party! Banger!" The party is at this house, hosted by a 16-year-old girl. As many as 50 teenagers have gathered to celebrate the end of summer. There are no parents at home. Jane doe knows trent through mutual friends. She had asked trent to come to that party specifically. Yes. Reporter: But ma'lik is meeting her for the first time. Would you call it a wild party? Yes. Reporter: Were people getting drunk? Well, everybody was drinking. But I wouldn't say, like, drunk drunk. Reporter: One person who witnesses agree is drunk is jane doe. She's had a red slushy spiked with vanilla vodka, a smirnoff malt liquor and several shots. Just after midnight, the host's 24-year-old brother comes home. He is a volunteer football coach at big red. He breaks up the party, sending drunken teenagers out into the night. He lates tells police he did not see any intoxicated teens. In exclusive police interviews obtained by "20/20," the teenage partiers recount what they remember. Jane doe's best friend says she is determined to leave with trent. I went out and tried to stop her. I was like, you're not leaving with them. And she was like, no, I'm going with them. She's done this before. I was like, she's not doing this again. Reporter: And how did the victim seem to you? Fine. She was just a little angry at her friends and telling them -- telling her friends to leave her alone and she's fine. Reporter: Even though she has stopped drinking, the effects of the alcohol continue to worsen. Jane doe gets into a car with trent, ma'lik and two other boys for the ten-minute drive to the house of another big red football player. I could tell that she was gradually getting more drunk and worse throughout the night. Like, that she couldn't walk. Reporter: As soon as she arrives at the second house, jane doe goes to the bathroom and gets sick. It is all steubenville high school people. Yeah. The victim is from west virginia. Report . She's isolated. She's alone. She's the most vulnerable because she's that intoxicated. Reporter: At this house, the only opportunity for a parent to step in slips away. When the mother at home says any teen not sleeping over has to leave. It is as they all leave that this infamous photo of trent, ma'lik and jane doe is taken. How did that picture come to be taken? Her ex-boyfriend said he wanted to get a picture of this drunk b. Reporter: How did she get into that position? She was willing to give him the picture that way, ma'am. We asked her. And that's when she said, "yeah, it's fine." Reporter: What was she doing when you asked her that question? She was -- she was just, like, laughing. We were all just talking, just clowning around. Reporter: Once again, concerned girls at this second house plead with jane doe not to leave with the boys. But they don't call for help. She wanted to go with trent and, like, we just kept trying to tell her, you don't want to do this, you don't want to go with them. And I just let her do what she wanted, which I understand was wrong. Reporter: Now, outside the second house, a disturbing scene. Jane doe sitting in the street, vomiting, surrounded by a group of laughing boys. And she throws up on her blouse and she takes her blouse off. Reporter: She took her blouse off? Yes. Reporter: All by herself? Yes. Reporter: Why did she do that? Because she had flew up all over her blouse. I gave her my jacket. There was a lot of people just around her, laughing. Reporter: Laughing? Yes. Just laughing about her, like, throwing up and laying in the street. Reporter: The humiliation continues when a boy offers $3 to anyone who will urinate on her. A joke, he says, that nobody takes him up on. I mean, I just kind of heard people go, piss on her. Reporter: And this is all on the street, right outside this house? Yes. Reporter: Where there is a parent home. Correct. Correct. Reporter: And nobody came out to the street to see what all the commotion was? Nobody came out of the house to say, hey, what's going on? Nobody got her water, nobody said, hey, I'll take her home, let's get her home. Reporter: Instead, that same group of deep teens gets back into the car for another ten-minute drive to their final destination of the night. The home of yet another big red football player. Ma'lik is in the front seat, jane doe and trent are in the back. Is there anything going on in the backseat? The music was up, ma'am, so, I really -- I couldn't hear nothing. Reporter: Playing on the radio that night? A rap song called "way too gone." &#9834; Way too gone &#9834; &#9834; what am I doing &#9834; &#9834; wake in the morning &#9834; &#9834; who the &#9834; Reporter: An am them for a night that has already gone way too far and is about to cross the line from crass to criminal. We were in the car, trent asked me to make a video of him and I did. Of him fingering her? Yes. Reporter: Under ohio law, jane doe has just been raped. What was trent doing? Well, trent was rubbing on her breast and she was kissing his neck and then he was, like, trying to unbutton her pants. Reporter: Did she seem to be responsive at all? No. She was just kissing on trent's neck. Reporter: So, she wasn't unconscious. No, ma'am. Reporter: Around 1:15 in the morning, the group heads to the basement of the house, where jane gets sick again. At this point, weren't you think, she must be really drunk? I really couldn't tell you. Reporter: So, you weren't thinking that a girl who keeps repeatedly throwing up was pretty drunk? No, because it's natural. Reporter: You see that a lot? Yeah. Reporter: At parties? Not just at parties. You see it everywhere. You can see that at a football game. You can see that at a concert. You can see that anywhere. Reporter: And even though other witnesses says she looked way out of it, that she was stumbling and slurring her words, you never saw her stumbling and slurring? No. Reporter: Ever during that sb entire night? No. She was having problems with coordination, vomiting. She was very drunk. And they had to have known it. Reporter: Nevertheless, another sexual assault is about to occur, and this time, witnesses say, ma'lik goes from being a bystander to a participant. What's the very first thing that happens when you go downstairs. They started fingering her on the floor and they were both fingering her. Reporter: On this issue, ma'lik's attorney would not allow him to comment. What I'm saying is that nothing happened that evening nonconsensual. There is no evidence to suggest that she was unconscious while laying there naked on that basement floor. Reporter: But other witnesses that night say she was very, very impaired, that she was stumbling, falling over. How is that not heavily intoxicated girl? No witness ever used the word impaired. Reporter: You don't think being drunk means being impaired? Substantially impaired to the point where you can't consent is the issue. Reporter: But this witness items police during the assault in the basement, the girl is unresponsive and that trent takes nude photos of her, creating more digital evidence that will eventually lead to his conviction. That's what I was trying to tell him, you need to, you know, please go to sleep, stop. Reporter: But it doesn't stop. That same teenager later items police he takes out hiss phone, you take while you were at the house? Ah, there were two. Reporter: Those pictures would eventually be deleted, but not before other boys see them, including michael nodianos, who reacts with that repulsive 12-minute rant. She's at least 14. She's more -- she's deader than a door nail. Reporter: A video that was the tinderbox for the whole case, made by someone who would later tell police he wasn't even at the scene of the crime. Were you there at all when she's in the house?

This transcript has been automatically generated and may not be 100% accurate.

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